Several types of closures or fasteners are available that permit repeated opening and reclosing of the fastener. They may be commonly used on packages and bags, but may also be used on other substrates such as clothing, boxes, shoes, diapers, pockets, or folders to suggest but a few examples. For example, it is common to use mechanical reclosable fasteners, such as slider zippers, clips, tabs, interlocking strips, and the like. These mechanical closures can be bulky, complex structures that require separate molding and fabrication steps prior to being joined to the various substrates. If used on flexible packages, the film rolls or other packaging materials incorporating such fasteners can be unwieldy and difficult to handle due to the added bulk from the fastener(s). Such fasteners can also add significant material and production costs to a package. In applications in which an air-tight or hermetic seal is desired, prior mechanical-based fasteners may also not form a sufficient airtight seal upon closure. When in a closed position, slider zippers can have an undesirable small air channel or gap due to bridging of interlocking flanges between an end-stop and the slider. Other mechanical interlocking fasteners may also have small air gaps and other spaces between the opposing portions that may allow air passage over time. When used on flexible packaging, mechanical fasteners can be applied in form, fill, and seal operations; however, such a process can require complex manufacturing steps to apply, interconnect, and align the features of each structure. For at least these reasons, mechanical reclosable fasteners can add undue complexity, cost, and expense into the manufacture of such packages while providing less than desirable reclosable capabilities in many applications.
Adhesive-based reclosable fasteners provide one alternative to the mechanical fasteners discussed above. Adhesive-based fasteners, however, present other challenges in both the manufacture, formation, and repeated use thereof. For example, pressure-sensitive adhesives (PSAs) may be useful as a one-time or permanent fastener; however, common PSA materials generally have relatively high tack levels rendering the adhesive as an undesired reclosable fastener. Tack is a property of an adhesive material that generally enables the material to form a bond with the surface of another material upon brief or light pressure. Tack is often considered as a quick stick, an initial adhesion, or a quick grab characteristic of a material. The high tack levels of many PSAs may, in some cases, result in shortcomings when attempting to use the PSAs as a reclosable fastener because the high tack generally does not permit the fastener to be easily opened and reclosed multiple times because the adhesive tends to be too sticky. The high tack levels of many PSAs may also cause shortcomings when attempting to run PSA coated materials on common processing equipment such as: blocking where the material does not unwind freely from a roll due to unacceptable back-side adhesion; picking where there is undesirable and unintended transfer of adhesive material to equipment surfaces, such as rollers, mandrels and filling tubes; poor tracking, such as the inability of the material to stay in proper alignment as it passes through the packaging machine; and jamming where the material is unable to slide over equipment surfaces and binds up.
If used as a fastener in situations where debris and contamination may come into contact with the adhesive, the resealability of the PSA fastener may tend to diminish. For example, if the fastener comes into contact with a crumbly product (i.e., a cookie, cracker, and the like), a shredded product (i.e., shredded cheese and the like), a fatty product, or a product with fine particulate, then the high tack levels of many PSAs may cause the crumbs or shreds to stick to the fastener, which reduces the effectiveness of the adhesive to form a fastener due to contamination of the PSA surface from the debris. A PSA fastener that is contaminated with product (examples noted above) will generally not form an adequate seal because the crumbs or other debris that are adhered to the PSA generally do not allow the PSA to adhere to the other side of the fastener in a repeated fashion.
On the other hand, lower tack PSAs generate other concerns when formed into a reclosable fastener. By its very nature, a lower tack adhesive is designed to have a reduced ability to stick to other surfaces, and lower tack adhesives can be difficult to adhere to a substrate surface due to its low tack properties. Thus, fasteners created with low tack PSAs may result in delamination of the PSA from the substrate surface upon opening or separating of the fastener. Even with low tack PSA adhesives, in some cases, fouling off the fastener with moisture, lipids, and very fine particulate can still result in a fastener that does not reseal effectively. Thus, when used as a fastener, low tack adhesive based reclosable fasteners may still present problems when a consumer attempts to reclose the fastener if it has come into contact with fatty or lipid containing foods, powdery foods, foods with topical seasonings, roast and ground coffee, shredded cheese, and powdered beverages, to suggest a few examples, because these materials can still reduce the effectiveness of the fastener.